System and method for natural gas dehydration

ABSTRACT

A natural gas dehydration system and method includes a contactor, a flash tank, and a still interconnected by a desiccant circulation system. A reboiler is coupled to the still and the flash tank to burn the flash gas from the flash tank and heat the desiccant. A secondary burner is associated with a vent stack of the reboiler to burn the flash gas from the flash tank when not firing the reboiler.

PRIORITY CLAIM

This is a continuation-in-part of U.S. patent application Ser. No.13/081,709, filed Apr. 7, 2011; which claims priority to U.S.Provisional Patent Application No. 61/322,022 filed on Apr. 8, 2010;which are hereby incorporated herein by this reference in theirentirety.

BACKGROUND

1. Field of the Invention

The present invention relates generally to natural gas dehydration.

2. Related Art

Natural gas from underground resources is commonly mixed with otherhydrocarbons, such as ethane, propane, butane and pentanes; water vapor;hydrogen sulfide; carbon dioxide; helium; nitrogen; etc. The gas isoften transported through a network of pipelines that can stretchthousands of miles. The gas is usually processed to separate the varioushydrocarbons and fluids to produce pipeline quality dry natural gas. TheGas Processors Association sets forth pipeline quality specificationsfor gas that the water content should not exceed 7 lb/million standardcubic feet (“MMSCF”). The natural gas from underground resources usuallycontains a large amount of water, and can be completely saturated. Thewater can cause problems to the pipeline, such as freezing at lowtemperatures, and forming hydrates with carbon dioxide and hydrocarbonsthat can clog equipment and pipes or cause corrosion.

While most of the water is removed from the natural gas at the wellheadby simple methods, dehydration units are often used to remove the watervapor from the gas. One method of removing water vapor utilizes a liquiddesiccant dehydrator, such as a glycol dehydrator. Glycol, which has anaffinity for water, is used to absorb the water vapor from the naturalgas. The natural gas and glycol are brought together in a contactor. Thedesiccant or glycol bearing the water out of the contactor is referredto as rich or wet and becomes heavier and sinks to the bottom of thecontactor where it is removed. The gas with the water vapor removed isreferred to as dry gas and exits the contactor to a storage tank. Smallamounts of methane and other compounds can also be found in the glycol.A flash tank can also be used to decrease the amount of methane andother compounds by reducing the pressure of the glycol allowing themethane and other hydrocarbons to vaporize or flash. The rich or wetglycol is feed to a stripper or regenerator with a column or still, anoverhead condenser, and a reboiler. The stripper or regeneratorvaporizes the water vapor, which has a boiling point of 212 degreesFahrenheit while glycol has a boiling point of 400 degrees Fahrenheit.One problem with prior art strippers or regenerators is that thereboiler runs sporadically, i.e. turns on and off, such that the glycoltemperature can vary by 50 degrees.

Dehydrations system also commonly use a jet-gas system which requires alarge mass flow of dry jet gas to drive hot glycol circulation in thewinter.

Enhancement methods to dehydration systems often involve lowering thepressure in the system to increase stripping, using a vacuum to lowerthe entire stripper pressure, using stripping gas, using a recoverablyhydrocarbon solvent, or withdrawing partially condensed vapors from thebulk liquid in the reboiler.

In addition, cold climates require more thorough and expensive glycoldehydration. Furthermore, new environmental regulations require theremoval of BTEX (benzene, toluene, ethylene and xylene) compounds fromthe still vents of natural gas dehydrators.

Improving the dehydration process is an ongoing endeavor.

SUMMARY OF THE INVENTION

It has been recognized that it would be advantageous to develop anultra-low emission glycol dehydration unit. In addition, it has beenrecognized that it would be advantageous to develop a dehydration unitthat utilizes flash gas in the reboiler; maintains glycol temperature;eliminates the jet-gas system for hot glycol circulation; uses a flashgas contactor to provide usable fuel gas to the reboiler, even duringthe winter; utilizes a glycol pump to circulate hot glycol heat traceduring the winter that can be bypassed in the summer; and resists orprevents the release of flash gas.

The invention provides a natural gas dehydration system including acontactor, a flash tank, and a still interconnected by a desiccantcirculation system. Dry desiccant (such as a lean tri-ethylene glycol(TEG)) enters the contactor along with wet gas to absorb water vapor andleave the contactor as wet desiccant (such as a rich TEG). The wetdesiccant enters and leaves the flash tank with flash gas separating inthe flash tank. The wet desiccant enters the still with the water vaporvaporizing, and leaves as dry desiccant returning to the contactor. Areboiler is coupled to the still and the flash tank to burn the flashgas from the flash tank and heat the desiccant. A burner associated withthe vent stack burns flash gas when not firing the reboiler.

In accordance with a more detailed aspect of the present invention, thesystem includes a flash gas contactor disposed on the flash tank andcoupled to the dry desiccant.

The invention provides a method for dehydrating natural gas, includingcirculating a desiccant (such as TEG) between a contactor, a flash tankand a still with a reboiler. Wet gas is introduced into the contactorwith dry desiccant (such as lean TEG) absorbing water vapor from the wetgas resulting in a wet desiccant (such as rich TEG) and dry gas. Flashgas is extracted from the wet desiccant in the flash tank. The watervapor is removed from the wet desiccant in the still by heating the wetdesiccant to vaporize the water vapor resulting in the dry desiccant.The dry desiccant is recirculated from the still to the contactor. Thereboiler is fired with the flash gas from the flash tank. The flash gasis burned in a burner associated with a vent stack of the reboiler whennot firing the reboiler.

In accordance with a more detailed aspect of the present invention, themethod includes bleeding dry, hot desiccant to a flash gas contactor onthe flash tank.

BRIEF DESCRIPTION OF THE DRAWINGS

Additional features and advantages of the invention will be apparentfrom the detailed description which follows, taken in conjunction withthe accompanying drawings, which together illustrate, by way of example,features of the invention; and, wherein:

FIG. 1 a is a process flow diagram of a natural gas dehydration systemin accordance with an embodiment of the present invention;

FIG. 1 b is a schematic diagram of the dehydration system of FIG. 1 a;

FIG. 2 is a schematic process flow diagram of the dry or lean glycolprocess flow of the dehydration system of FIG. 1 a;

FIG. 3 is a schematic process flow diagram of the wet or rich glycolprocess flow of the dehydration system of FIG. 1 a;

FIG. 4 is a schematic process flow diagram of the dehydrated gas or drygas process flow of the dehydration system of FIG. 1 a;

FIG. 5 is a schematic process flow diagram of the fuel gas process flowof the dehydration system of FIG. 1 a; and

FIG. 6 is a schematic process flow diagram of the fuel gas process flowof the dehydration system of FIG. 1 a.

Reference will now be made to the exemplary embodiments illustrated, andspecific language will be used herein to describe the same. It willnevertheless be understood that no limitation of the scope of theinvention is thereby intended.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENT(S)

As illustrated in FIGS. 1 a-6, a natural gas dehydration system,indicated generally at 110, in an example implementation in accordancewith the invention is shown for dehydrating natural gas. Such a systemcan be used in the field at remote operations adjacent one or more wellheads for processing natural gas prior to transporting in a pipeline.Alternatively, the system can be used with a plant and can venthydrocarbon vapors to a relief or fuel gas system. The system can be anultra-low emission glycol dehydration unit that can sufficientlydehydrate raw, compressed natural gas to less than 7 lbs water/MMSCF gaswith total hydrocarbon (THC) emissions of less than six tons per year.In contrast, normal THC emissions are 20 to 80 tons per year. Inaddition, the system can provide up to 12 MMSCFD of rich gas at 300 PSIGoperating pressure, or up to 40 MMSCFD of lean gas at 1000 psigoperating pressure. The system can be an absorption type dehydrationsystem using a liquid desiccant, such as glycol or TEG.

Generally speaking, the system 110 can include a contactor 114, a flashtank 118, and a stripper or regenerator 122 with a still 126, anoverhead condenser 130 and a reboiler 134. A desiccant or TEGcirculation system 138 can interconnect the various components with pipeor tubing. The contactor 114 can be coupled to a wet gas source 142,such as a compressor discharge, and a lean TEG source, such as still 126or stripper or regenerator 122. In addition, the contactor 114 iscoupled to a dry gas storage, such as the pipeline 146 or tank, and arich TEG outlet that can be coupled to the stripper or regenerator 122.Dry or lean TEG enters the contactor 114 along with wet gas with the TEGabsorbing water vapor from the wet gas. After absorbing the water vapor,the TEG becomes wet or rich TEG and accumulates at the bottom of thecontactor where it leaves or is withdrawn. The gas with the water vaporremoved becomes dry gas and leaves or is withdrawn from the contactor.Thus, lean TEG enters the contactor, absorbs water vapor and leaves thecontactor as rich TEG. Similarly, wet gas enters the contactor, has itswater vapor absorbed by the TEG, and exits the contactor as dry gas. Thewet gas may first pass through an inlet gas separator 150 coupledbetween the gas source 142 and the contactor 114. The dry gas leavingthe contactor and the lean TEG entering the contactor can pass through agas/glycol heat exchanger 154 which heats the dry gas and cools the leanTEG.

A pump 158 can be coupled to the TEG circulation system to pump lean TEGinto the contactor and rich TEG out of the contactor. The wet TEG iswithdrawn from the contactor and directed to the flash tank 118 whereflash gas separates from the wet TEG. The flash tank 118 can be coupledto rich TEG outlet of the contactor, and can have a rich TEG outlet anda flash gas outlet. The rich TEG can pass through a glycol/glycol heatexchanger 162 along with lean TEG from the stripper on the way to thecontactor where the rich TEG temperature is increased and the pressuredecreased. For example, the rich TEG temperature can increase 100 to 110degrees, such as from 92 to 100 degrees Fahrenheit.

In addition, a flash gas contactor 166 can be coupled to the flash tank118. The flash gas contactor 166 can be coupled to the source of leanTEG to the contactor 114 and an outlet for the flash gas. A heat traceand a heat trace bypass can be coupled in-line between the lean TEG tothe flash gas contactor 166. The flash gas can be coupled to a fuel gasscrubber 188 and outlet to a fuel tank or pipeline, which in turn, canbe coupled to the reboiler 134 as discussed below. The flash gascontactor provides usable fuel gas to the re-boiler, even during winterconditions.

The rich TEG leaving the flash tank can pass through one or morefilters, such as a glycol filter 170 and a glycol charcoal filter 174 toremove impurities that may clog or foul piping or equipment. Inaddition, the rich TEG can pass through a glycol/glycol heat exchanger178 coupled to the lean TEG from the stripper to the contactor. Again,the rich TEG temperature is increased and the pressure decreased. Forexample, the lean TEG temperature can increase 130-140 degrees, such asfrom 188 to 325 degrees Fahrenheit. Thus, from the contactor 114 to thestripper 122 or still 126, the rich TEG temperature can increase 230-240degrees.

The rich TEG enters the still 126 and the water vapor vaporizes. Thestill 126 is coupled to the rich TEG outlet of the flash tank. The watervapor can vent out the top of the still to the overhead vapor condenser130 that is also coupled to the dry gas leaving the contactor. The watervapor can be accumulated in a liquid accumulator 182 with any waste gasvented or flared, and the liquid pumped to a condensate storage tank186.

The reboiler 134 takes TEG in the still, heats it, and returns it to thestill. Heating the TEG causes the water vapor to boil off the TEG. Thereboiler 134 can be coupled to the flash tank and can burn the flashgas. All of the flash gas can be burned in the reboiler 134, withoutventing or flaring the flash gas. The reboiler can be configured topreferentially consume glycol flash gas over make-up fuel gas. Thereboiler 134 can be a continuously fired reboiler that maintains thetemperature of the TEG. A control system can be coupled to the reboiler134 to maintain a temperature of the TEG above a predetermined minimumtemperature. As described above, prior art reboilers operatesporadically, resulting in temperature differences of up to 50 degreesin the TEG. When the TEG and/or the reboiler 134 is at operatingtemperature, or when not firing the reboiler (or burner thereof), theflash gas or excess flash gas can be burned in a secondary burner 190associated with a vent stack 194 of the reboiler. Thus, excess flash gasis burned rather than vented to the atmosphere. In one aspect, thesecondary burner can be carried by the vent stack, and the secondaryburner can be coupled to the vent stack at an angle (e.g. substantially45 degrees) so that the secondary burner exhausts into the vent stack.The lean or dry TEG is withdrawn from the still into a glycol tank, anddirected back to the contactor 114 through the heat exchangers 178 and162 and pump 158. In addition, the heat trace can bleed off the lean TEGto the flash gas contactor 166. The pump 158 is used to circulate hotTEG through the heat trace during winter operation, and can be by-passedduring summer operation.

Hydrocarbon liquids are removed from the separator, accumulator, glycolflash tank, fuel-gas system and power-gas system.

A method for dehydrating natural gas, and for using the system describedabove, includes:

1) introducing wet gas with water vapor and lean TEG into a contactor114 and allowing the lean TEG to absorb water vapor from the wet gasresulting in rich TEG with water vapor and dry gas;

2) extracting the dry gas and the rich TEG from the contactor;

3) introducing the rich TEG into a flash tank 118;

4) separating flash gas from the rich TEG in the flash tank;

5) directing the rich TEG from the flash tank to a still 126 with areboiler 134;

6) heating the rich TEG in the reboiler to vaporize the water in therich TEG resulting in dry TEG;

7) directing the dry TEG from the still back to the contactor 114;

8) heating the TEG by firing the reboiler 134 with the flash gas fromthe flash tank; and

9) burning flash gas in a burner 190 associated with a vent stack 194 ofthe reboiler when not firing the reboiler with the flash gas.

The temperature of the TEG in the reboiler can be maintained within atleast a 50 degree temperature range. In addition, the TEG can becontinuously heated by continuously firing the reboiler. In addition,hot, dry TEG from the still can be circulated to a flash gas contactor166 disposed on the flash tank 118, such as during winter. The TEG canbe pumped through the circulation system, and through the heat trace tothe flash gas contactor, with a pump, and without a jet gas system.Furthermore, the flash gas can be washed, particularly in the winter, toremove moisture and heavy hydrocarbons. In addition, all of the flashgas can be burned in the reboiler, without venting or flaring the flashgas.

In addition, a method for dehydrating natural gas, and for using thesystem described above, includes:

-   -   a) circulating a desiccant between a contactor 114, a flash tank        118 and a still 126 with a reboiler 134;    -   b) introducing wet gas into the contactor with dry or lean        desiccant, the dry or lean desiccant absorbing water vapor from        the wet gas resulting in a rich or wet desiccant and dry gas;    -   c) extracting flash gas from the rich or wet desiccant in the        flash tank;    -   d) removing the water vapor from the rich or wet desiccant in        the still by heating the rich or wet desiccant to vaporize the        water vapor resulting in the dry or lean desiccant;    -   e) recirculating the dry or lean desiccant from the still to the        contactor;    -   f) firing the reboiler with the flash gas from the flash tank;        and    -   g) burning flash gas in a burner 190 associated with a vent        stack 194 of the reboiler when not firing the reboiler with the        flash gas.

With specific reference now to FIG. 1 a, the following tables representoperational parameters related to different components of one embodimentof the present invention.

TABLE 1 Stream No. 4 1 2 3 Super- 5 Units of Wet Gas From Wet Gas toContactor heated Dry Gas Description Measure Compressor Contactor OVHDDry Gas to Pipeline Temperature F. 90 90 95 101 105 Pressure PSIA 365365 364.5 359.5 358.5 Vapor Fraction 0.9690 1.0000 1.0000 1.0000 1.0000Mass Flow LB/HR 14692.33 13149.93 13149.93 13149.93 13146.13 Molar flowMOL/HR 67.6000 666.2707 664.5014 664.5014 664.3094 STD Gas Flow MMSCFD6.2623 6.0681 6.052 6.052 6.0502 Liq. Vol Flow GPM — — — — — FlowingDensity LB/FT³ 1.480 1.340 1.320 1.280 1.260 MOL. WT LB/LB-MOL 21.3719.83 19.79 19.79 19.79 TEG LB/HR 0.00 0.00 0.01 0.01 0.01 H20 LB/HR23.79 23.51 1.86 1.86 1.86 Methane LB/HR 9578.40 9541.26 9540.01 9540.019537.25 Ethane LB/HR 629.26 617.83 617.61 617.61 617.43 Propane LB/HR605.24 572.28 571.54 571.54 571.38 Butanes LB/HR 797.75 692.20 691.37691.37 691.18 Benzene LB/HR 107.21 38.10 24.55 24.55 24.55 Toluene LB/HR63.23 9.91 2.25 2.25 2.25 Xylenes LB/HR 199.12 11.43 2.00 2.00 2.00

TABLE 2 Stream No. 6 7 9 11 13 Lean Rich Rich Rich Rich Units of TEG toTEG from TEG to TEG to TEG to Description Measure Contactor ContactorFlash Tank Filters still column Temperature F. 100 92 200 188 325Pressure PSIA 373.4 365 45 45 25 Vapor Fraction 0.0000 0.0000 0.01020.0000 0.0154 Mass Flow LB/HR 1690.93 1754.42 1754.42 2074.91 2074.91Molar flow MOL/HR 12.4281 14.1974 14.1974 164661 16.4661 STD Gas FlowMMSCFD — — — — — Liq. Vol Flow GPM 3.01 3.16 3.28 3.87 — Flowing DensityLB/FT³ 70.120 69.260 36.030 66.790 17.190 MOL. WT LB/LB-MOL 136.06123.57 126.57 126.01 TEG LB/HR 1663.52 1663.50 1663.50 1982.17 1982.17H20 LB/HR 23.70 45.35 45.35 49.88 49.88 Methane LB/HR 0.00 1.25 1.250.11 0.11 Ethane LB/HR 0.00 0.22 0.22 0.04 0.04 Propane LB/HR 0.00 0.740.74 0.33 0.33 Butanes LB/HR 0.00 0.82 0.82 0.39 0.39 Benzene LB/HR 0.0013.55 13.55 13.55 13.55 Toluene LB/HR 0.05 7.70 7.70 7.71 7.71 XylenesLB/HR 3.67 13.10 13.10 13.81 13.81

TABLE 3 Stream No. 15 17 21 14 LN TEG to 16 LN TEG LN TEG to Units of LnTEG from Cold TEG LN TEG Pump Flash Gas Description Measure Reboiler HXRTo Pump Disch. Contactor Temperature F. 385 250 149 151 120 PressurePSIA 18 17 15 390 277 Vapor Fraction 0.0000 0.0000 0.0000 0.0000 45.0000Mass Flow LB/HR 2012.02 2012.02 2012.02 2012.02 321.10 Molar flow MOL/HR14.7877 14.7877 14.7877 14.7877 2.3600 STD Gas Flow MMSCFD — — — — —Liq. Vol Flow GPM 4.05 3.81 3.66 3.65 0.65 Flowing Density LB/FT³ 61.92065.890 68.610 68.820 69.540 MOL. WT LB/LB-MOL 136.06 136.06 136.06136.06 136.06 TEG LB/HR 1979.37 1979.37 1979.37 1979.37 315.89 H20 LB/HR28.19 28.19 28.19 28.19 4.50 Methane LB/HR 0.00 0.00 0.00 0.00 0.00Ethane LB/HR 0.00 0.00 0.00 2.00 0.00 Propane LB/HR 0.00 0.00 0.00 0.001.00 Butanes LB/HR 0.00 0.00 0.00 0.00 0.00 Benzene LB/HR 0.00 0.00 0.000.00 0.00 Toluene LB/HR 0.05 0.05 0.05 0.05 0.01 Xylenes LB/HR 4.40 4.404.40 4.40 0.71

TABLE 4 Stream No. 25 28 41 22 23 Waste Gas Cond. Total Units of FlashGas Still Column to Flare From Cond/Water Description Measure to FuelOVHD Vent or ATM Separator to Tank Temperature F. 121 325 110 90 72Pressure PSIA 44.5 17.5 15.5 365 45 Vapor Fraction 1.0000 1.0000 0.00000.0000 0.1478 Mass Flow LB/HR 3.46 60.10 0.93 1478.91 1540.87 Molar flowMOL/HR 0.1123 1.6784 0.0211 21.3292 22.9865 STD Gas Flow MMSCFD 0.0010.0153 0.0002 — — Liq. Vol Flow GPM — — — 4.65 — Flowing Density LB/FT³0.220 0.080 0.110 39.610 3.360 MOL. WT LB/LB-MOL 30.8 37.47 44 69.3467.03 TEG LB/HR 0.00 0.01 0.00 0.00 0.01 H20 LB/HR 0.01 21.69 3.03 11.4211.44 Methane LB/HR 1.14 0.11 0.11 37.14 37.15 Ethane LB/HR 0.18 1.040.03 11.42 11.44 Propane LB/HR 0.42 0.33 0.13 32.96 33.15 Butanes LB/HR0.45 0.39 0.07 105.55 105.87 Benzene LB/HR 0.00 13.55 0.18 69.10 82.47Toluene LB/HR 0.00 7.65 0.03 53.33 60.95 Xylenes LB/HR 0.00 9.41 0.01187.68 197.07

In addition, the following callout numbers have been used specificallyin connection with FIG. 1 a and have their attendant definitions. V-605refers to a fuel gas scrubber, V-601 refers to an inlet gas separator,T-601 refers to a glycol contactor, E-603 refers to a gas/glycolexchanger, P-601 refers to cold glycol/glycol exchanger, V-602 refers toa glycol flash tank, T-603 refers to a flash gas contactor, F-601 refersto a glycol filter, V-602 refers to a glycol flash tank, T-603 refers toa flash gas contactor, F-602 refers to a glycol charcoal filter, V-603refers to a glycol surge tank, E-602 refers to a hot glycol/glycolexchange, E-604 refers to still column vapor condenser, T-602 refers toa glycol still, H-601 refers to a glycol reboiler, V-604 refers to aliquid accumulator, and P-602 refers to an accumulator pump.

While the forgoing examples are illustrative of the principles of thepresent invention in one or more particular applications, it will beapparent to those of ordinary skill in the art that numerousmodifications in form, usage and details of implementation can be madewithout the exercise of inventive faculty, and without departing fromthe principles and concepts of the invention. Accordingly, it is notintended that the invention be limited, except as by the claims setforth below.

1. A method for dehydrating natural gas, comprising: a) circulating adesiccant between a contactor, a flash tank and a still with a reboiler;b) introducing wet gas into the contactor with dry or lean desiccant,the dry or lean desiccant absorbing water vapor from the wet gasresulting in a rich or wet desiccant and dry gas; c) extracting flashgas from the rich or wet desiccant in the flash tank; d) removing thewater vapor from the rich or wet desiccant in the still by heating therich or wet desiccant to vaporize the water vapor resulting in the dryor lean desiccant; e) recirculating the dry or lean desiccant from thestill to the contactor; f) firing the reboiler with the flash gas fromthe flash tank; and g) burning flash gas in a burner associated with avent stack of the reboiler when not firing the reboiler with the flashgas.
 2. A method in accordance with claim 1, further comprising:circulating dry or lean desiccant from the still to the flash tank.
 3. Amethod in accordance with claim 1, further comprising: circulating dryor lean desiccant from the still to the flash tank with a heat traceduring winter operation; and by-passing the heat trace during summeroperation.
 4. A method in accordance with claim 1, further comprising:directing dry or lean desiccant from the still to a flash gas contactoron the flash tank.
 5. A method in accordance with claim 1, furthercomprising pumping the desiccant with a pump, and without a jet gassystem.
 6. A method in accordance with claim 1, further comprising:washing the flash gas to remove moisture and heavy hydrocarbons in thewinter.
 7. A method in accordance with claim 1, further comprising:passing rich or wet desiccant after the contactor and before the flashtank through a heat exchanger along with dry or lean desiccant from thestill on the way to the contactor; and passing rich or wet desiccantafter the flash tank and before the still through another heat exchangeralong with dry or lean desiccant from the still on the way to thecontactor.
 8. A method in accordance with claim 1, further comprising:maintaining a temperature of the desiccant in the reboiler within atleast a 50 degree temperature range.
 9. A method in accordance withclaim 1, further comprising: burning all of the flash gas in thereboiler without venting or flaring the flash gas.
 10. A method fordehydrating natural gas, comprising: a) introducing wet gas with watervapor and lean tri-ethylene glycol (TEG) into a contactor and allowingthe lean TEG to absorb water vapor from the wet gas resulting in richTEG with water vapor and dry gas; b) extracting the dry gas and the richTEG from the contactor; c) introducing the rich TEG into a flash tank;d) separating flash gas from the rich TEG in the flash tank; e)directing the rich TEG from the flash tank to a still with a reboiler;f) heating the rich TEG in the reboiler to vaporize the water in therich TEG resulting in dry TEG; g) directing the dry TEG from the stillback to the contactor; h) heating the TEG by firing the reboiler withthe flash gas from the flash tank; i) burning flash gas in a burnerassociated with a vent stack of the reboiler when not firing thereboiler with the flash gas.
 11. A method in accordance with claim 10,further comprising: circulating dry TEG from the still to the flashtank.
 12. A method in accordance with claim 10, further comprising:circulating dry TEG from the still to the flash tank with a heat traceduring winter operation; and by-passing the heat trace during summeroperation.
 13. A method in accordance with claim 10, further comprising:directing dry TEG from the still to a flash gas contactor on the flashtank.
 14. A method in accordance with claim 10, further comprising:maintaining a temperature of the TEG in the reboiler within at least a50 degree temperature range.
 15. A method in accordance with claim 10,further comprising pumping the TEG with a pump, and without a jet gassystem.
 16. A method in accordance with claim 10, further comprising:washing the flash gas to remove moisture and heavy hydrocarbons in thewinter.
 17. A method in accordance with claim 10, further comprising:burning all of the flash gas in the reboiler without venting or flaringthe flash gas.
 18. A natural gas dehydration system, comprising: a) acontactor, a flash tank, and a still interconnected by a desiccantcirculation system with dry desiccant entering the contactor along withwet gas to absorb water vapor and leave the contactor as wet desiccant,the wet desiccant entering and leaving the flash tank with flash gasseparating in the flash tank, and the wet desiccant entering the stillwith the water vapor vaporizing and leaving as dry desiccant returningto the contactor; and b) a reboiler coupled to the still and the flashtank to burn the flash gas from the flash tank and heat the desiccant;and c) a burner associated with a vent stack of the reboiler to burn theflash gas from the flash tank when not firing the reboiler.
 19. A systemin accordance with claim 18, further comprising: a heat trace coupledin-line between the dry desiccant returning to the contactor and theflash tank.
 20. A system in accordance with claim 19, furthercomprising: a heat trace bypass coupled in-line between the drydesiccant returning to the contactor and the flash tank.
 21. A system inaccordance with claim 18, further comprising: a flash gas contactordisposed on the flash tank.
 22. A system in accordance with claim 18,further comprising: the burner being coupled to the vent stack of thereboiler at substantially a 45 degree angle.